Method for making artificial snow

ABSTRACT

A method of making artificial snow by mixing water with a surfactant, the surfactant preferably forming 0.03% to 5% of the mixture by weight; aerating the mixture to form a foam of bubbles; and freezing the foam to form the snow crystals. The mixture is preferably aerated with air in the ratio water:air in the range 1:2 to 1:3 (v/v). The foam of bubbles is frozen by laying it over a refrigerated grid laid over the skiing slope and the foam is preferably laid and frozen in layers until the desired depth of snow is achieved.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a method for making artificial snow, and to asnow skiing slope using such snow.

(2) Prior Art

In certain skiing resorts, man-made slopes are created usingsnow-machines which spray water and compressed air in a careful-ycontrolled atmosphere (for both temperature and humidity) to create ablanket of snow. These machines are expensive to operate and theatmosphere is difficult to control, requiring expensive air conditioningequipment. The man-made slopes generally only extend the operating lifeof the slope by approximately 30 days.

In more temperate areas, artificial slopes are created using mats ormat-like layers of e.g. "Dendex", "Delta" or "Dri Sno" (trade marks)materials. These slopes require the use of special skis and poles andcannot truly re-create a snow-covered slope.

In International Application No. PCT/AU85/00267 (Bucceri) there isdisclosed a method for making artificial snow by mixing water with awater swellable polymer to approximately 50-70% of the maximum waterretention capacity of the polymer, aerating the mixture and freezing themixture to produce snow crystals which can be laid on a refrigeratedfloor to form a skiing slope. This method has proved very effective butin certain applications the cost of the polymer is a disadvantage.

SUMMARY OF THE PRESENT INVENTION

It is an object of the present invention to provide a method of makingartificial snow which is relatively simple and inexpensive.

It is a preferred object to provide a method where the snow can be laidin layers e.g. of different crystal size or where a layer of "powdersnow" can be laid over a harder base snow.

It is a further preferred object to provide a method where the water canbe recovered, and the snow refrozen, as required.

It is a still further preferred object to provide a ski-slopeincorporating the snow produced by the present invention.

Other preferred objects of the present invention will become apparentfrom the following description.

In a broad aspect the present invention resides in a method for makingartificial snow including the steps of:

mixing water with a surfactant (i.e. surface-active-agent or wettingagent);

agitating, aerating and/or bubbling gas through the mixture to form afoam or froth of water bubbles;

applying the foam or froth of bubbles to the area on which theartificial snow is to be created; and

freeze the foam or froth of bubbles to form the snow crystals.

Suitable surfactants include soaps and detergents; sulphated, aliphaticor aromatic alcohols; linear or branched chain alkybenzene sulphonates;alkyarine sulphonates; sodium dodecylbenzene sulphonate; alkylsulphonates; anionic, cationic and non-ionic surfactants.

Non-ionic surfactants are preferred as these form a resilient foam withsmall/minute bubbles which on freezing, produce high quality snowcrystals down to powder snow size. Preferably the surfactant forming0.03% to 5% of the mixture by weight. For environmental reasons,bio-degradable surfactants are preferred.

A bulk volume of the mixture may be agitated or aerated to produce afoam of bubbles on top of the mixture and the foam may be transferred ortransported to the area where the snow is to be created. The mixture maybe aerated by pumping air through the mixture at the ratio water:air 1:1to 1:5 (v/v), the preferred aeration range being 1:2 to 1:3 (v/v).

Alternatively, the mixture may be mixed and sprayed from equipment ofthe type used for fire fighting foam (i.e. a foam generator), the foamof bubbles being sprayed over the area where the snow is to be created.

The foam may be laid over a skiing slope and frozen by the cold ambientair or may be laid over an area covered by a flexible cover or structureinto which is pumped cold air or refrigerant. The foam may also be laidover artificial snow formed by the method of International ApplicationNo. PCT/AU85/00267 to form a layer of powder snow. Preferably the foamis laid over a refrigerated grid so that the bubbles break downthemselves into the snow crystals. (The mixture is frozen from thebottom upwardly and the weight of the foam above the frozen bubblesassists in breaking down the bubbles into the snow crystals.)

Smaller bubbles may be preferred as these are more persistent (i.e. lesslikely to break before freezing) and more ice crystals are produced. Thefrozen bubbles may be compressed or crushed by passing a roller over thebubbles.

BRIEF DESCRIPTION OF THE DRAWINGS

To enable the invention to be fully understood, a number of preferredembodiments will now be described with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic view of a first embodiment; and

FIG. 2 is a schematic view of a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, water and linear chain alkylbenzene sulphonate arestored in separate W, S tanks, and are mixed in a mixing head M in aratio of e.g. 97% water:3% sulphonate and sprayed from a foam nozzle Nof a foam generator FG used to spray fire fighting foam, the foammixture being sprayed in the form of a foam of bubbles, the foam beinglaid in layers 10 over the area of the proposed ski slope 11.

The bubbles have a skin with a low gas permeability and so the entrainedair in the bubbles cannot readily escape. The ambient air e.g. below -5°C. causes the skins of the bubbles to freeze to form a frozen foam ofbubbles with the air remaining entrained.

A roller is passed over the frozen layer to break the frozen bubbleskins, releasing the air, and compressing the bubbles to form snowcrystals.

The resulting artificial snow has skiing characteristics similar tonatural snow and by varying the size of the bubbles, the nature of thesnow in the different layers can be varied to suit the desiredconditions.

Referring to FIG. 2, water and the surfactant e.g. detergent from tanks,W,S are mixed in the mixing head M in the ratio 99% water:1% surfactantand the mixture is aerated by pumping air into the mixing head M fromair air compressor AC at the ratio of water:air equals 1:2(volume/volume).

The resultant foam of bubbles is laid over a frozen flexible grid system20 (e.g. of the type sold under the "Icemat" trade mark by CalmacManufacturing Corporation, of Englewood, N.J., U.S.A.--the subject ofU.S. Pat. Nos. 3,751,935 and 3,893,507), the flexible grid system 20being cooled by a refrigeration unit R. The bubbles in the foam freezefrom the bottom upwards and break down into the snow crystals which forma layer 21 over the grid. To build up the desired thickness of snow,additional layers of foam are laid down and allowed to freeze to formsnow crystals.

If the ambient air temperature is not low enough to freeze the foam ofbubbles, cold air e.g. in the form of a curtain may be blown over thefoam (see FIG. 1). Alternatively, a flexible cover 30 (see FIG. 2) maybe laid over the foam and cold air or refrigerant (e.g. fromrefrigerator unit 12) may be pumped through or under the cover 30 tofreeze the foam.

In another embodiment, the mixture may be aerated with air to form thefoam and then frozen by passing CO₂ gas through the foam.

At the end of the ski season, when the air temperature is above 0° C.,the snow will melt and if a biodegradable surfactant has been used,little, if any, ecological damage will occur to the surroundings. Acatchment may be provided at the base of the ski-slope 11 to collect themelt snow.

To enable the skiing surface to be maintained, the surface may be"shaved", the removed snow melted and refrozen and laid or a fresh layerof the snow crystals may be laid over the existing surface. Bycontrolling the percentage of surfactant and the aeration of themixture, the fresh layer can comprise powder snow crystals.

It will be readily apparent to the skilled addressee that a wide rangeof suitable surfactants may be used and that many alternative methodsfor mixing the constituents, generating the foam of bubble, and layingthe foam, are available without departing from the scope of the presentinvention defined in the appended claims.

I claim:
 1. A method for making artificial snow including the stepsof:mixing water with a surfactant; agitating, aerating and/or bubblinggas through the mixture to form a foam or froth of water bubbles;applying the foam or froth of bubbles as a substantially unfrozen layerto the area on which the artificial snow is to be created; and freezingthe foam or froth of bubbles to form snow crystals.
 2. A method asclaimed in claim 1 wherein: the surfactant comprises one or more fromthe group: soaps and detergents; sulphated, aliphatic or aromaticalcohols; linear or branched chain alkylbenzene sulphonates; alkylarinesulphonates; sodium dodecylbenzene sulphonate; alkyl sulphonates;anionic, cationic and non-ionic surfactants.
 3. A method as claimed inclaim 1 or 2 wherein:the surfactant forms 0.03% to 5% of the mixture byweight.
 4. A method as claimed in claim 1 wherein:the mixture is aeratedby air in the ratio water:air in the range 1:1 to 1:5 (volume/volume).5. A method as claimed in claim 4 wherein:the ratio water:air is in therange 1:2 to 1:3 (volume/volume).
 6. A method as claimed in claim 1wherein:the foam of bubbles is laid over a refrigerated grid system on askiing slope, the bubbles in the foam freezing and breaking down intothe snow crystals.
 7. A method as claimed in claim 1 wherein:the foam ofbubbles is laid over a skiing slope and the foam of bubbles is frozen bythe cold ambient air.
 8. A method as claimed in claim 1 wherein:the foamof bubbles is laid over a skiing slope and is covered by a flexiblecover, and cold air or refrigerant is pumped through or under the coverto freeze the foam of bubbles.
 9. A method as claimed in claim 1wherein:the foam of bubbles is frozen by pumping CO₂ gas through theaerated mixture.
 10. A method as claimed in claim 1 wherein:the mixtureis aerated in a fire fighting foam generator and the foam of bubbles issprayed over the skiing slope from a nozzle attached to the foamgenerator.
 11. A method as claimed in claim 1, wherein:the frozenbubbles are compressed or crushed to form the snow crystals.
 12. Amethod as claimed in claim 8, wherein:said refrigerant is pumped throughthe cover to freeze the foam.
 13. A method as claimed in claim 1,wherein:the foam of bubbles is laid over a skiing slope and is coveredby a flexible cover, and cold air is pumped under the cover to freezethe foam of bubbles.
 14. A method as claimed in claim 13, wherein:saidcold air is pumped through the cover to freeze the foam of bubbles. 15.A skiing slope including:a refrigerated floor or grid; and at least onelayer of snow crystals covering the floor or grid, the snow crystalsbeing made by a method including the steps of: mixing water with asurfactant; forming a foam of the resulting mixture; applying the foamas a substantially unfrozen layer to cover the floor or grid; andfreezing the foam to form snow crystals.